1 files changed, 183 insertions, 0 deletions
diff --git a/src/ARMeilleure/CodeGen/Optimizations/Simplification.cs b/src/ARMeilleure/CodeGen/Optimizations/Simplification.cs
new file mode 100644
index 00000000..a439d642
--- /dev/null
+++ b/src/ARMeilleure/CodeGen/Optimizations/Simplification.cs
@@ -0,0 +1,183 @@
+using ARMeilleure.IntermediateRepresentation;
+using System;
+using static ARMeilleure.IntermediateRepresentation.Operand.Factory;
+
+namespace ARMeilleure.CodeGen.Optimizations
+{
+    static class Simplification
+    {
+        public static void RunPass(Operation operation)
+        {
+            switch (operation.Instruction)
+            {
+                case Instruction.Add:
+                    if (operation.GetSource(0).Relocatable ||
+                        operation.GetSource(1).Relocatable)
+                    {
+                        break;
+                    }
+
+                    TryEliminateBinaryOpComutative(operation, 0);
+                    break;
+
+                case Instruction.BitwiseAnd:
+                    TryEliminateBitwiseAnd(operation);
+                    break;
+
+                case Instruction.BitwiseOr:
+                    TryEliminateBitwiseOr(operation);
+                    break;
+
+                case Instruction.BitwiseExclusiveOr:
+                    TryEliminateBitwiseExclusiveOr(operation);
+                    break;
+
+                case Instruction.ConditionalSelect:
+                    TryEliminateConditionalSelect(operation);
+                    break;
+
+                case Instruction.Divide:
+                    TryEliminateBinaryOpY(operation, 1);
+                    break;
+
+                case Instruction.Multiply:
+                    TryEliminateBinaryOpComutative(operation, 1);
+                    break;
+
+                case Instruction.ShiftLeft:
+                case Instruction.ShiftRightSI:
+                case Instruction.ShiftRightUI:
+                case Instruction.Subtract:
+                    TryEliminateBinaryOpY(operation, 0);
+                    break;
+            }
+        }
+
+        private static void TryEliminateBitwiseAnd(Operation operation)
+        {
+            // Try to recognize and optimize those 3 patterns (in order):
+            // x & 0xFFFFFFFF == x,          0xFFFFFFFF & y == y,
+            // x & 0x00000000 == 0x00000000, 0x00000000 & y == 0x00000000
+            Operand x = operation.GetSource(0);
+            Operand y = operation.GetSource(1);
+
+            if (IsConstEqual(x, AllOnes(x.Type)))
+            {
+                operation.TurnIntoCopy(y);
+            }
+            else if (IsConstEqual(y, AllOnes(y.Type)))
+            {
+                operation.TurnIntoCopy(x);
+            }
+            else if (IsConstEqual(x, 0) || IsConstEqual(y, 0))
+            {
+                operation.TurnIntoCopy(Const(x.Type, 0));
+            }
+        }
+
+        private static void TryEliminateBitwiseOr(Operation operation)
+        {
+            // Try to recognize and optimize those 3 patterns (in order):
+            // x | 0x00000000 == x,          0x00000000 | y == y,
+            // x | 0xFFFFFFFF == 0xFFFFFFFF, 0xFFFFFFFF | y == 0xFFFFFFFF
+            Operand x = operation.GetSource(0);
+            Operand y = operation.GetSource(1);
+
+            if (IsConstEqual(x, 0))
+            {
+                operation.TurnIntoCopy(y);
+            }
+            else if (IsConstEqual(y, 0))
+            {
+                operation.TurnIntoCopy(x);
+            }
+            else if (IsConstEqual(x, AllOnes(x.Type)) || IsConstEqual(y, AllOnes(y.Type)))
+            {
+                operation.TurnIntoCopy(Const(AllOnes(x.Type)));
+            }
+        }
+
+        private static void TryEliminateBitwiseExclusiveOr(Operation operation)
+        {
+            // Try to recognize and optimize those 2 patterns (in order):
+            // x ^ y == 0x00000000 when x == y
+            // 0x00000000 ^ y == y, x ^ 0x00000000 == x
+            Operand x = operation.GetSource(0);
+            Operand y = operation.GetSource(1);
+
+            if (x == y && x.Type.IsInteger())
+            {
+                operation.TurnIntoCopy(Const(x.Type, 0));
+            }
+            else
+            {
+                TryEliminateBinaryOpComutative(operation, 0);
+            }
+        }
+
+        private static void TryEliminateBinaryOpY(Operation operation, ulong comparand)
+        {
+            Operand x = operation.GetSource(0);
+            Operand y = operation.GetSource(1);
+
+            if (IsConstEqual(y, comparand))
+            {
+                operation.TurnIntoCopy(x);
+            }
+        }
+
+        private static void TryEliminateBinaryOpComutative(Operation operation, ulong comparand)
+        {
+            Operand x = operation.GetSource(0);
+            Operand y = operation.GetSource(1);
+
+            if (IsConstEqual(x, comparand))
+            {
+                operation.TurnIntoCopy(y);
+            }
+            else if (IsConstEqual(y, comparand))
+            {
+                operation.TurnIntoCopy(x);
+            }
+        }
+
+        private static void TryEliminateConditionalSelect(Operation operation)
+        {
+            Operand cond = operation.GetSource(0);
+
+            if (cond.Kind != OperandKind.Constant)
+            {
+                return;
+            }
+
+            // The condition is constant, we can turn it into a copy, and select
+            // the source based on the condition value.
+            int srcIndex = cond.Value != 0 ? 1 : 2;
+
+            Operand source = operation.GetSource(srcIndex);
+
+            operation.TurnIntoCopy(source);
+        }
+
+        private static bool IsConstEqual(Operand operand, ulong comparand)
+        {
+            if (operand.Kind != OperandKind.Constant || !operand.Type.IsInteger())
+            {
+                return false;
+            }
+
+            return operand.Value == comparand;
+        }
+
+        private static ulong AllOnes(OperandType type)
+        {
+            switch (type)
+            {
+                case OperandType.I32: return ~0U;
+                case OperandType.I64: return ~0UL;
+            }
+
+            throw new ArgumentException("Invalid operand type \"" + type + "\".");
+        }
+    }
+}
+\ No newline at end of file